It is well known to apply Ellipsometry to characterize Physical and Optical properties of Samples. It is also known that while Temperature changes affect Samples, detection of said changes thereof using electromagnetic radiation is often difficult. For instance, plots of Optical Constants vs. wavelength often change very little with temperature.
A known Patent which describes monitoring Temperature of a sample using a Rotating Compensator Ellipsometer is U.S. Pat. No. 6,596,404 to Wei et al.
Other Patents found in a Search for key-words (Ellipsometry and Temperture) are:                U.S. Pat. No. 6,583,875;        U.S. Pat. No. 6,563,591;        U.S. Pat. No. 6,596,404;        U.S. Pat. No. 6,509,200;        U.S. Pat. No. 6,459,126;        U.S. Pat. No. 6,436,541;        U.S. Pat. No. 6,317,216;        U.S. Pat. No. 6,300,638;        U.S. Pat. No. 6,277,657;        U.S. Pat. No. 6,211,961;        U.S. Pat. No. 6,090,442;        U.S. Pat. No. 6,008,906;        U.S. Pat. No. 6,837,108;        U.S. Pat. No. 6,688,585;        U.S. Pat. No. 6,282,925;        U.S. Pat. NO. 6,770,924; and        U.S. Pat. No. 6,277,320.        
A paper of relevance is that by Balmer et al., titled “Substrate Temperature Reference Using SiC Absorption Edge Measured by In Situ Spectral Reflectometry, J. of Crystal Growth, 248, (2003). This paper describes application of Reflectometry to determine substrate temperature.
Another paper, Titled “Investigation of Half-Wave Method for Birefringence or Thickness Measurements of a Thick, Semitransparent, Uniaxial, Anisotropic Substrate by Use of Spectroscopic Ellipsometry”, Kildemo et al., Appl. Optics., Vol. 30, No 25, (2000), describes application of Ellipsometry to investigate Birefringence in substrates.
Another paper titled “Advanced Process Control for High Quality R & D and Production of MOVPE Material by RealTem”, Malm et al., J. of Crystal Growth, 248, (2003) describes determination of temperature of a wafer by measuring the emmissivity of a wafer using an infra-red pyrometer with a pulsed laser-based reflectometer, both working at 905 nm and positioned at normal incidence to wafers inside a Metalorganic Vapor Phase Epitaxy (MOVPE) system.
The method disclosed herein for monitoring Temperature Change in Uniaxial or Biaxial Anisotropic Samples which utilizes change in birefringence electromagnetic radiation provides benefit over the prior art.